Over at "Frontal Cortex," Jonah Lehrer recently wrote about why commuting makes us so unhappy. Well those of us who commute by foot have plenty to complain about too. And, according to new research, it appears we're quite justified.

A group of "crowd physicists"—the best job I've heard of since assistant to the traveling secretary—has found that up to 70 percent of walkers travel in groups. As the researchers report in PLoS One (full study), this sidewalk socializing slows down foot traffic by roughly 17 percent:

These insights demonstrate that crowd dynamics is not only determined by physical constraints induced by other pedestrians and the environment, but also significantly by communicative, social interactions among individuals.

The researchers found that when people walking in groups run into space problems, they shift into convex V-shapes to facilitate socialization. These V's, according to the researchers, "do not have optimal 'aerodynamic' features."

In case you were wondering, this is what your stroll looks like to a crowd physicist:

(That dot at the end must mean my shoelace is untied.)

A previous study by several of the same authors (pdf here) found that problems arise even when we walk alone:

In case of head-on encounters, a binary decision takes place: pedestrians need choose whether to evade the other person on the right-hand or on the left-hand side. This decision process goes along with a significant decrease of walking speed. ... It is therefore advantageous for an individual to develop the same preference as the majority of people.

The Headcase, for one, believes we could remove "preference" from the equation by holding walkers to the rules of the road. Let's face it: In the current sidewalk regime, walking is a free-for-all. I'm constantly weaving in and out of stop-and-chatters. I'm lifting my arm to pass shorter people and small children. Oh I'll use the bus lane. Seriously, what other aspect of society allows such unfettered chaos? Hell, even banks might get regulated.

The aforementioned papers are mathematically based, but I see sidewalk congestion as a largely psychological problem. As a result, I suspect much of it could be solved with a simple behavioral Nudge: painting lane lines on sidewalks.

Think about it. Most people would instantly fall into predictable traffic flows. The system could mature from there: A high-speed, singles passing lane on the left. A slower, two-person lane on the right (the bizarro H.O.V. lane). The beauty of this plan is its simplicity.

Threes remain a problem, but three is a problem in driving too, with one person stuck in the back. The fastest walker would naturally take the driver position. (Do you hop into the Accord when there's a Boxster in the garage?) Standing talkers would be ticketed, just like drivers on cell phones. Move it to the storefronts, people. I'll stop short of proposing a Walker's License, although, if nothing else, a Dept. of Bodily Vehicles would create jobs.

The biggest foreseeable puzzle is how to minimize the pile-ups that occur when people wait at curbs to cross. I propose keeping a one-body distance from the person in front of you, so opposing traffic can pass, though admittedly this could get complicated. But hey, that's why we have crowd physicists.

(Image: Courtesy Mehdi Moussaid, via Science)

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